1. Field of the Invention
The present invention relates to a pipe joining method for joining pipes together, and to a junction structure for joining pipes. In particular, the present invention relates to a method for joining pipes and a junction structure for joining pipes when one of the pipes is formed from a thermoplastic resin.
Priority is claimed on Japanese Patent Application No. 2009-58023, filed Mar. 11, 2009, the contents of which are incorporated herein by reference.
2. Description of Related Art
Conventionally, various methods and structures have been proposed for joining pipes together. Specifically, these relate to methods for joining together a first pipe that is made of metal and a second pipe that is made of thermoplastic resin. For example, a method has been proposed in which an outer circumferential surface of a first pipe is coated with an adhesive agent which is made of the same type of resin as the resin used to form a second pipe. The first pipe is then inserted into the second pipe, and the two are heated and then cooled (see, for example, Japanese Unexamined Patent Application, Publication No. H5-271626). According to this method, the junction between the first pipe and the second pipe can be made strong and airtight.
Another structure has been proposed in which a toroidal projection is provided on an outer circumference of one pipe, and a toroidal depression is provided in an inner circumferential surface of the other pipe. When the one pipe is inserted into the other pipe, the projection engages with the depression (see, for example, Published Japanese Translation No. 2000-503749 of the PCT International Publication). According to this type of structure a join is easily achieved as, simply by inserting one pipe into the other pipe, the projection is engaged with the depression and the two pipes are joined together.